1. Field of the Invention
The present invention relates to fire retardant cellulosic webs and the internal treatment therefor. More especially, the present invention pertains to the manufacture of construction boards by laminating a plurality of such webs together.
2. Description of the Prior Art
It has long been a major endeavor to produce fire retardant construction materials which exhibit reduced combustion tendencies with respect to both the flash point of the material and the generation of noxious, often toxic, gaseous combustion products. Limited success has been realized by the incorporation of antimony trioxide or various chlorinated hydrocarbons, the latter often times applied in a paint or as a coating for the exterior surfaces of construction paneling. While these fire retardant materials have provided a limited measure of success, it has been found that the antimony trioxide additions significantly increase cost of construction panels incorporating the same. Significantly also, it has been found that the chlorinated hydrocarbons (e.g. chlorinated paraffins) have a marked tendency to decompose during combustion and emit chlorine gas. In order to minimize generation of this toxic product, it has, thus, been mandated that some types of stabilizer additionally be provided.
The plastics industry has similarly been plagued with numerous problems regarding the combustibility of resinous materials. One approach to reduce the combustible tendencies of resinous materials has been the incorporation of an inorganic filler, such as a hydrated oxide, which aids in the reduction of flash point and the generation of noxious or toxic combustion products. That is, such hydrated oxides will absorb heat, thus lowering the overall temperature of the article in which incorporated, and release the water of hydration as innocuous steam. See, for example, U.S. Pat. Nos. 3,741,929 and 3,827,997.
Notwithstanding the apparent success of these prior art techniques to provide a measure of fire retardancy to various materials, the prior art does not recognize analogous treatment of construction boards, most notably cellulosic construction boards, to improve their fire retardant characteristics. In part, this may be attributed to the highly functional nature of uniformity of board caliper and/or waterproofing characteristics versus the interaction between filler additions and degree of compression. Accordingly, the need exists to provide cellulosic construction boards exhibiting improved fire retardancy in a simple, yet highly effective, efficient, and economical manner.